#include <bits/stdc++.h>
using namespace std;

int N;
int A[5], B[5];
int C[5], D[5];

int cal(int x) {
	int sum = 1;
	for (int i = 1; i <= x; i++) sum *= i;
	return sum;
}

int main() {
	cin >> N;
	for (int i = 1; i <= N; i++) cin >> A[i];
	for (int i = 1; i <= N; i++) cin >> B[i];
	for (int i = 1; i <= N; i++) C[i] = i;
	int ans = 0;
	do {
		for (int i = 1; i <= N; i++) D[i] = i;
		do {
			int a = 0, b = 0;
			for (int i = 1; i <= N; i++) {
				if (A[C[i]] < B[D[i]]) b++;
				else if (A[C[i]] > B[D[i]]) a++;
			}
			if (a > b) ans++;
		} while(next_permutation(D + 1, D + N + 1));
	}while(next_permutation(C + 1, C + N + 1));
	cout << fixed << setprecision(10) << (double)((1.0 * ans) / (1.0 * cal(N) * cal(N))) << endl;
	return 0;
}